Greg,
Two disagreements with "proposed solutions".
Both of these are based on some crystal-ball-gazing and a desire to
not specify things in MIME that lock us into old habits which some folks
see as becoming obsolete.
I'm sending these as separate notes, with separate topics, to make
things easier to follow.
6) Message/Partial send over an 8 bit or binary path cannot be
converted in a MIME aware gateway from 8 bits to 7 bits due to the
prohibition on encoding of the message content type and the unknown
nature of the content
Proposed Solution: Prohibit the sending of message/partial with any CTE
other than 7 bit.
Alternate suggestion: Make an exception to the nested encoding rule in
this case, requiring an implementation that can't manage to do things in
one pass to unpack and then combine, rather than combining and
unpacking.
Rationale:
(1) If 8bit transport is worth anything, even to some of the people some
of the time, these presumably large messages are exactly the places
where the "save transport size" and "save bandwidth" arguments become
important.
(2) If one believes, as some do, that 8bit transport will eventually
take over the world and 7bit will become the exception, putting this
constraint into MIME locks us into a technology that would otherwise
gradually become obsolete.
(3) For very large messages, unpack and then combine might be the
practice on many hosts anyway for reasons having to do with storage
management and a desire to accept the maximum possible final message
sizes.
--john